1. Field of the Invention
The invention relates to the field of ducted fan propulsion systems and, in particular, to a ducted fan propulsion system for toy vehicles and the like.
2. Description of Related Art
In any propulsion system that uses combustion exhaust thrust to produce directly forward velocity, maximum efficiency is achieved when the forward velocity of the vehicle equals the velocity of the exhaust. This is why a helicopter is more efficient when hovering than a vertical, takeoff-and-landing aircraft such as the AV-8A Harrier aircraft and a propeller driven aircraft more efficient than a jet powered aircraft at low speed. The same principle applies for toy vehicles.
However, no rocket powered toy car or aircraft is ever going to be operating at speeds where any degree of propulsive efficiency will be achieved. Yet, toy solid propellant rocket engines come in many convenient sizes and "pack" a lot of energy into a very small, light-weight and inexpensive package. Thus, they are very attractive for use in toy dragsters and the like. They are much lighter in weight than the commonly used high pressure, carbon dioxide cartridges, which only come in one basic size. Using a conventional two-cycle, internal combustion engine to power a ducted fan would create an expensive, heavy and complicated propulsion system. Thus, a propulsion system that combines the high energy source of a solid propellant rocket motor with the low speed efficiency of a fan would provide the best of two worlds, at least as a toy vehicle power plant.
The only known significant prior art that combines solid propellants with a jet engine is the use of a solid propellant gas generator to start the engine. In this application the combustion products are ducted to and drive the turbine blades. The turbine drives the compressor up to a speed sufficient to produce enough pressure in the combustion section such that the engine becomes operational on its own. However, propulsive forces are not generated.
Thus, it is a primary object of the subject invention to provide a solid propellant rocket motor powered ducted fan engine.
It is another primary object of the subject invention to provide a solid propellant rocket motor powered ducted fan engine wherein the rocket motor also provides a significant portion of the total thrust.
It is a further object of the subject invention to provide a propulsion system for toy vehicles and the like.